The present invention is directed to a water level indicator for use in a nuclear power plant.
During maintenance periods at a nuclear power plant, it is important for safety reasons to know the level of water in the hot leg of the water line travelling from the reactor vessel to the heat exchanger to ensure proper reactor core cooling. Present methods of measuring the water in this particular pipe have proven inadequate because of inaccuracies in the measurement of the water level in the pipe or the inability to make the water level reading from the control room of the power plant.
During nuclear plant operation, water is heated under pressure in the reactor vessel. The water then travels through the hot leg pipe of the water circulation system to the heat exchanger/steam generator where the water is cooled. The cooled water then travels through a circulation pump to be returned to the reactor vessel for reheating. The water serves as the medium to cool the reactor core and transfer heat to the heat exchanger steam generator.
During maintenance periods, water needs to be drained from the heat exchanger/steam generators to facilitate examination of the generator's internal equipment. While the steam generator does not serve its heat exchanging function during these maintenance periods, the water is cooled by another heat exchanger as the water continues to function as a coolant for the core. Since the hot leg pipe lies in essentially a horizontal plane, the precise level of water in the pipe is important. Should the water in the pipe be too high, or full, the inside of the generator, where work crews are performing examinations, could be flooded. Should the water level in the hot leg pipe be too low, or empty, this could indicate a water level too low to maintain proper cooling of the nuclear core. Because the hot leg has a direct fluid connection to the reactor vessel, the hot leg is in a convenient position for measuring the water level to ensure proper water level in the core. Therefore, being able to measure the precise water level in the hot leg pipe is of crucial importance for safety. It is of additional safety consideration that the level may be measured from the nuclear plant's control room where other safety equipment is monitored.